Global research trends related to coronavirus disease 2019 and the aged: a bibliometric analysis

ABSTRACT BACKGROUND: A bibliometric analysis covering only the production of original studies or considering world production until 2022 has yet to be conducted. The creation and advancement of vaccines have also influenced research priorities, demonstrating the need for a new approach to this subject. OBJECTIVES: To analyze worldwide scientific production related to coronavirus disease 2019 (COVID-19) and the aged and to describe what has already been produced. DESIGN AND SETTING: Bibliometric analysis with a quantitative approach. METHOD: The search terms “COVID-19,” “SARS-CoV-2,” “Aged,” and “Elderly” were used to retrieve articles from the Web of Science database. A total of 684 articles were included in the analysis. Data were imported into RStudio Desktop Software and linked to R Software. The Bibliometrix R package and VOSviewer software were used for analysis. RESULTS: Most articles were published in 2020. These were produced by 4,937 authors and published in 379 journals. The keyword most used by the authors was “COVID-19.” Publications from 77 countries were obtained. China had the highest article production ranking, and Spain collaborated the most. The articles addressed the implications of the pandemic on the aged, the relationship between vaccination in the aged, and the implications for the disease itself. CONCLUSION: Further research should be conducted, mainly concerning vaccines and vaccination of the aged, owing to the need for and importance of immunization in this risk group, including assessing the long-term effects of vaccines.

quantitative analysis of articles in each field so that their results can support the realization of future studies. 10 A bibliometric analysis covering only the production of original studies or contemplating world production until 2022 is yet to be conducted. 11,12 Additionally, the creation and advancement of vaccines have also influenced research priorities, demonstrating the need for a new approach to the subject. 5

OBJECTIVE
This study analyzed worldwide scientific production related to COVID-19 and the aged and described what has already been produced.

Research design
This bibliometric analysis used a quantitative approach.
Bibliometrics is a discipline that seeks to measure scientific and social activity and predict trends through literature analysis conducted using the following steps: research design, a compilation of bibliometric data, data analysis, data visualization, and interpretation of results. 13,14 Data-gathering period A search for scientific articles was conducted using an advanced query in the Web of Science™ (WoS) database on October 31, 2022. WoS is among the most reliable and comprehensive databases for bibliometric studies, allowing the tracking of ideas across disciplines and a time of nearly 1.9 billion references cited in more than 171 million records. 15

Selection criteria
The included studies met the following criteria: original research on COVID-19 and the aged, without language restrictions, and published until October 31, 2022. As exclusion criteria: articles that deviated from the research scope, review articles, opinion articles, reflection articles, editorials, and case studies.

Data-gathering
Before starting the research, the descriptors "COVID-19, " "SARS-CoV-2, " and "Aged" were obtained in the Medical Subject Headings (MeSH), including the alternative descriptor "Elderly" often used to refer to the aged in the scientific literature. To ensure precise and targeted outcomes while minimizing false positives, the present research focused exclusively on the articles using the following search strategy: "TI=(("COVID-19" OR " SARS-CoV-2") AND ("Aged" OR "Elderly")). " The search yielded 1,466 articles; 968 had early or open access after filtering the originals. To ensure the inclusion of articles on the target topic and reduce false positives, the researchers read all titles and excluded those unrelated to COVID-19 and the aged. The remaining 684 contained all available information downloaded in text file format for analysis.

Data processing and analysis
The recovered data was imported into RStudio Desktop Software, In summary, the analysis allowed data visualization for later  "Elderly" (n = 160), and "SARS-CoV-2" (n = 86). Other words that stood out were: "mortality, " "older adults, " "pandemic, " "depression, " "coronavirus, " "mental health, " "aged, " "frailty, " and "anxiety. " Considering the co-occurrence of terms in frequency ≥ 10 and relating the title to the abstract, 397 terms were found from 14,170 expressions. Figure 3 shows 60% (n = 238) of the most relevant terms. The VOSviewer Software divides the terms into three main clusters, identified by the colors red, blue, and green. Noteworthy, the size of the item's circle or node is proportional to the number of times a given item appears.
The evaluated articles had an average citation count of 7.7%, using 18 434 references. In ranking the most cited articles (Table 1)  Authors from 77 countries participated in the articles, as recognized by the Bibliometrix. Figure 4A shows the countries that produced the most, considering the co-occurrence of these countries in the address list of each author, and that, consequently, may be present more than once. China occupied the top position of production by being present 373 times, followed by Italy with 329, the United States with 262, Spain with 246, and France with 204 registrations. Countries such as Germany, Australia, Brazil, and Japan also stand out.    Most authors have published only one article on this topic.
Therefore, according to Lotka's law, this area must be consolidated.
This law estimates that approximately 60% of authors will produce a single document, and a third of the literature will be produced by a tenth of the most productive authors. 18 Moreover, the percentage of authors who produced only one article may be even more significant than what was identified.
Notably, a high number of authors was noted in some articles, The third place was occupied by two other journals, one related to psychiatry and the other related to general health, each publishing ten articles. Thus, the authors preferred to publish their studies in a broad scope because, of the scientific journals that comprised the Bradford nucleus, only 10 had a specific scope for geriatrics, gerontology, or aging.
Keywords can summarize the focus of articles and determine research trends based on the analysis of these words. 37 In the current research, the authors' keywords mainly addressed the name of the disease and its variations, the name of the virus, problems related to the pandemic and the disease, factors that make the aged more susceptible, and words related to vaccines or vaccination.
Several names were used to refer to the aged, such as "Elderly, " "Older adults, " "Aged, " "Aging, " "Elderly patients, " "Elderly population," "Older people," "Elderly people," "Age," "Geriatrics." Noteworthy, such a diversity of names made it difficult to initially filter the articles, thus recommending the standardization of "Aged, " the primary term according to MeSH, or its alternative term, "Elderly. " According to the terms of the titles and abstracts of the articles, three topics were addressed:1 (red) implications of the pandemic on the aged, which triggered psychological problems such as depression and anxiety; 2 (blue) the relation of vaccine or vaccination in the aged; and 3 (green) implications of the disease itself, causing hospitalization to death, mainly in the studied population.
Regarding the most-cited articles, despite being recent, vaccines have already received many citations. Its effectiveness was addressed in three of the most cited articles, and the fourth addressed vaccination acceptance.
The most-cited article was a randomized, double-ano-  The limitations were how the bibliometric survey was conducted, including using a single database, and the rigor of the search adopted by contemplating only the titles of the articles.
Another limitation was the non-standardization of authors' names, which, owing to the similarity of names, may have influenced Lotka's law. However, the database used is a selective, structured, and balanced database with complete citation links and improved metadata that support a wide range of information purposes, allowing the development of scientometrics. 41 Regarding the search by title, studies have already described that it allows the recovery and specificity of the articles, generating minimal losses compared to the search that includes all fields. 42 Thus, synthesizing the research patterns related to COVID-19 and the international population can provide valuable insights into future research areas and perspectives. Thus, considering the current context of the COVID-19 pandemic, it is suggested that further research be conducted, mainly related to vaccines and vaccination of the aged, owing to the need for and importance of immunization in this risk group as well as the need to assess the long-term effects of vaccines.